Physical, environmental, and pharmacological stressors have been repeatedly shown to increase self-administration of various abused substances in both preclinical and human studies. The primary aim of the proposed work is to assess the effects of yohimbine, a pharmacological agent, used to create an objectively-measured stress response, upon opioid-seeking behavior and craving.

Participants will first be an outpatient and must come to the Jefferson Avenue Research Program daily to receive buprenorphine doses. This phase will last at least 10 days or longer. Three times per week during the first two weeks (i.e., on 6 different days), participants will be asked to provide urine samples and to complete questionnaires that ask about opiate withdrawal symptoms.

Next, participants will live on an inpatient research unit for at least 11 consecutive nights and possibly up to 15 consecutive nights. During this stay they will participate in a total of eight experimental sessions. Participants will take part in multiple trials in which they have the opportunity to choose drug, hydromorphone (HYD), or money. HYD is a drug that is currently used as a cough suppressant and to relieve pain. During the first two test sessions, participants will receive a sample of the drug doses that can be chosen. Before each of the final 6 test sessions begin, participants will be given a capsule containing either different doses of the drug yohimbine or a placebo (blank). Yohimbine is a drug that has been shown to produce a "stress"-like response in humans. Then participants will have 12 opportunities to choose either drug or money by using a computer to earn choices. Respiration rate, oxygen saturation, heart rate, and blood pressure will be monitored throughout choice trials. Self-report questionnaires will be completed at different times during the study.

After participants have completed the experimental procedures, they will again come to the Jefferson Ave. Research Program daily to receive buprenorphine doses. The dose of buprenorphine will be gradually decreased so that they will eventually be free from medication. This will take three weeks. We will administer questionnaires and collect urine samples three times each week to assess using illicit drugs.